RM to AU Converter
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Supports: RM
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Need help?RM to AU Converter
RM (RealMedia) is RealNetworks' legacy streaming container from the late 1990s and early 2000s, holding a RealVideo track, a RealAudio track, or both. AU (.au/.snd) is the Sun Microsystems audio format from 1992 — one of the oldest digital audio formats, historically tied to Unix workstations and Java. This converter is an audio extraction: it pulls the audio track out of the RM file and writes it to a standalone AU file. The video, if any, is discarded.
RM Format at a Glance
| Property | Value |
|---|---|
| Full name | RealMedia |
| Vendor | RealNetworks |
| Released | Late 1990s (popular through the early 2000s) |
| Type | Streaming container (audio + video) |
| Audio payload | RealAudio (RA), lossy |
| Video payload | RealVideo (RV) |
| VBR variant | RMVB (RealMedia Variable Bitrate) |
| Plays in | RealPlayer; VLC (partial support) |
| Status | Legacy / largely obsolete |
AU Format at a Glance
| Property | Value |
|---|---|
| Full name | Sun/NeXT audio (.au, .snd) |
| Vendor | Sun Microsystems |
| Released | 1992 |
| Header | 24-byte header beginning with the magic number .snd |
| Byte order | Big-endian |
| Original encoding | 8-bit μ-law (G.711) at 8000 Hz — the de facto Unix sound default |
| Other encodings | 8/16/24/32-bit linear PCM, A-law, ADPCM |
| Common sample rates | 8000, 11025, 22050, 44100, 48000 Hz |
| Associated with | Unix (/dev/audio), Java AudioClip |
| Best for | Old Unix systems and Java applets that expect .au input |
How to Convert RM to AU
- Upload Your RM File: Drag and drop your .rm file onto the page or click "+ Add Files" to select it from your computer. You can queue several files to extract audio from all of them with the same settings.
- Choose the AU Encoding: Open "Show All Options" to pick the AU codec — μ-law (8-bit, telephone-grade, smallest file) or signed 16-bit PCM (uncompressed, larger but full bandwidth). Big-endian PCM (s16be) is the most portable AU variant.
- Set Audio Sample Rate and Channel (Optional): Use "Audio Sample Rate" and "Audio Channel" to match a target system — for example 8000 Hz mono for a classic μ-law file, or leave both on "Original" to keep the source rate. "Trim" lets you export only part of the track.
- Convert and Download: Click "Convert" and download your AU file. Files are uploaded over an encrypted connection, processed on our servers, and deleted automatically after a few hours. No sign-up, no watermark.
Frequently Asked Questions
Does the AU file keep any video from the RM?
No. AU is an audio-only format, so the conversion extracts just the audio track from the RM container and discards the video. If you need the video too, convert the RM to a video format instead.
Will RM to AU restore the original audio quality?
No. RealAudio inside an RM file is already lossy, so detail discarded during the original encoding is gone for good. Converting to AU cannot recover it. If the AU output uses 8-bit μ-law, that adds a second round of lossy companding on top — fine for speech, but it narrows the bandwidth further. Choosing 16-bit PCM avoids that second loss but cannot improve on what the RealAudio source already contains.
What is the difference between μ-law and PCM in an AU file?
μ-law (8-bit, G.711) is logarithmic companding designed for telephony — it stores roughly 8 KB per second of audio, half the size of 16-bit PCM, at telephone-grade fidelity. Linear PCM (16/24/32-bit) is uncompressed: larger files, but it preserves the full bandwidth of the source. Pick μ-law for compatibility with old Unix or telephony systems, and PCM when fidelity matters more than size.
Why would anyone convert to AU instead of MP3 or WAV?
AU is a niche target today. The main reason to choose it is feeding an old Unix workstation, a legacy Solaris pipeline, or a vintage Java AudioClip that specifically expects .au input. For everyday playback on phones, browsers, and modern players, convert RM to MP3 is far more compatible, and convert RM to WAV is the standard uncompressed option.
What can open a .au file?
Cross-platform players such as VLC and foobar2000 open .au files, as do Apple QuickTime, Adobe Audition, and historically RealPlayer. On Unix systems .au was the native sound format via /dev/audio, and Java used it for applet audio. Because support is uneven on modern consumer devices, converting to MP3 or WAV is usually the safer route for general use.
Is the conversion private?
Yes. Your RM file is uploaded over an encrypted connection, processed on our servers, and deleted automatically after a few hours. Files are never shared or made public, there is no watermark, and no sign-up is required.
Can I extract audio from several RM files at once?
Yes. Add multiple .rm files to the queue and they are converted to AU with the same encoding, sample rate, and channel settings. In our testing, batching short RealAudio clips to 8000 Hz μ-law produced AU files only a few kilobytes per second of audio — the trade-off being telephone-grade fidelity rather than full bandwidth.
What sample rate and channel should I choose for the AU file?
To reproduce the classic Unix μ-law default, set the Audio Sample Rate to 8000 Hz and the Audio Channel to Mono — that is the historical telephone-grade .au configuration. For fuller fidelity, leave both on "Original" (commonly 44100 or 48000 Hz, stereo) and pick 16-bit PCM. Because the RealAudio source is already lossy, raising the sample rate above the original cannot add detail, so matching or keeping the source rate is the sensible choice.
For converting other RealMedia files, see the RM converter hub; to go the other way into AU from other sources, see the AU converter hub.